Method of producing expanded fabric-like material



Allg- 20, 1953 E. B. RICHMOND 3,100,926

METHOD oF PRoDUcING EXPANDED FABRIC-LIKE MATERAL original Filed April S, 1958 ai n u s ma IN VEN TOR.

EARL B. RICHMOND ATTOR N EY United States Patent O ltlo METHD @F PRUDUCENG EXPANDED FAlilslC-Lll@ MATERIAL Earl ll.' Richmond, West Covina, Calif., assigner to 'lille Electric Storage Battery Company, a corporation of New .l'ersey @riginal application Apr. 3, 1958, Ser. No. 726,199.

Bivided .and this application lune 23, lilou, Ser. No.

l Claims. (Cl. 28m-75) This `application is `a division of application Serial No. 726,190, tiled April 3, 1958.

The invention relates to new and improved methods of producing fabric-like materials, either woven, knitted, or non-Woven, and to the materials themselves which are of a new and improved type when compared to those presently known in the art.

More specically, the fabric-like materials of the invention are characterized by enhanced qualities of heat insulation and crash or impact absorption, such qualities being provided by the peculiar construction of the materialls. In addition, the fabric 'has extraordinary qualities of strength and resistance to unraveling, the threads of the material ybeing integrally and permanently bonded together at their points of juncture.

In its broadest sense, the present invention comprises the extrusion of a thread frorna mixture of a thermoplastic resin and a blowing agent, forming said extruded thread into a fabric-like material, and thermally treating said fabric to decompose the blowing agent Vthereby evolving gases which, in turn, have the duel effect of expanding the thermoplastic thread to produce a cellular type material and welding the thermally softened threads at their points of juncture in a permanent bond under the expansive forces caused by the gas evolution.

Additionally, the invention contemplates the production of a fabric-like material from a combination consisting of the type of thread described above `and another thread of a non-expandable character.

Another form of the invention may consist of a fabriclike material in which the threads that make up the material are expanded to different degrees.

ln connection with the description of my process and product that follows, reference is made to the attached drawing in which,

FIGURE l is an elevational view of a portion of a fabric material produced in accord-ance with the invention but before activation of the blowing agent;

FIGURE 2 is an elevational view of the material shown in FlGURE l after the blowing step has occurred;

FlGURE 3 is a cross sectional View taken along the lines 3-3 of FIGURE 2;

FGURE 4 is .an elevational View of an alternate form of the invention; and

FIGURE 5 is an elevational View of still another form of the invention.

In the practice of the invention, there can be utilized a number of conventional thermoplastic resins such as, for example, polyvinyl chloride, polyethylene, `and nylon. There can also be used copolymers of vinyl chloride 'and vinylidene chloride in which the latter substance is present in an `amount of up to about and copolymers of vinyl chloride and vinyl acetate in which the vinyl acetate is present in an amount up to about ln the case of polyvinyl chloride, it is suitable to use the material in the form of a vinyl plastiso-l, which is understood to be a dispersion of vinyl resin in a plasticizer, such as dioctyl phthalate, dibutyl phthalate, tricresyl phosphate, or the like. In the preparation of this plastisol, the vinyl resin can be physically `stirred into the plasticizer, the resulting mix being -in the form of a liquid having a viscosity determined by the various proportions of the resin and 3,1%,925 Patented Aug. 20, 1963 ICC plasticizer present in the mix. In the preparation of such a mix to be used in the present invention, I have found a proportion of parts by Weight of resin and 5 to 300 parts by weight of plasticizer to be satisfactory. A preferred mix is l0() parts by weight of resin to from 20 to 100 parts by Weightof the plasticizer.

It will be understood that to this mixture there can, if desired, be added a filler, such as a metal carbonate, or a clay in van amount of up to about 100 parts by weight, such filler acting as an extender for the vinyl resin and the plasticizer.

To the various mixtures described above, there is then added a blowing agent in a desired amount, such blowing agent being of the type that, when decomposed under applioationof heat, yields a gas that is compatiblewith the other constituents of the mixture. These blowing agents may, for example, `be of any conventional type commonly used in the gas expansion of thermoplastics and rubber. The only qualiiications are that they thermally decompose to produce a gas 'and leave a residue both of which are compatible with the other cc-nstitutents of the mixture. The specic blowing agents for a given mixture will be selected on the basis of the temperature at which decomposition will commence as the agent must not be decomposed vat extrusion temperatures. For example, since polyvinylchloride, and the mentioned copolymers, fis extrudable `'at a minimum temperature of 250 F., the blowing agent should not start to decompose at less than about 260 F. Additionally, blowing agents for mixtures containing polyethylene and nylon should not have a decomposition point of less than about 310 F. since those resinswill be extruded at a minimum of about 300 F. Blowing agents that have been found to be satisfactory 'are those sold under the trade names of Celogen and Gelegen-AZ by Naugatuck Chemical Company. The chemical name for Celogen is p,poxybis-(benzenesulfonyl hydrazide). Gelegen-AZ is an azodicarbonamide having a formula CN=NC(COOH)2. The specific type blowing agent to be used in this connection does not form part of this invention since many such useful materials are lavailable on the markets. The blowing agent used, however, will be present in the mix in an amount of from about 0.5 part by weight to about 50 parts by weight, preferably from about 3 parts to `about l0 parts, depending upon the desired degree of expansion and specic gravity of the final product.

It will be understood that conventional heat and light stabilizers of the organic or inorganic type can also be added to the mix-ture for-known purposes in an amount of about 1 to about 5 parts by weight, with 3 parts being preferred. For polyvinyl chloride, and the copolymers of vinylchloride and vinylidene chloride, these stabilizers may be salts of tin, lead, cadmium, or zinc. Also, organic stabilizers such as salts of fatty acids or mercapto derivatives of the metallic esters, are suitable. For polyethylene, an amine stabilizer will be used. Mixes of the following materials and proportions have been found to be suitable in the practice of the invention:

EXAMPLE 1 i (No Filler) Polyvinyl chloride resin- 100 parts by weight. -Dioctyl phthalate plasticizer 5 parts to 300 parts by weight (20 parts to 100 parts preferred). Celogen-AZ-blowing agent 0.5 part to .50 parts by weight (3 parts to 101 parts being preferred). Lead carbonate stabilizer-.." 1 pant to 5 parts by weight (3 parts preferred).

ticizen 3S EXAMPLE 2 (Filler) VLead carbonate stabilizer". l part to 5 parts by weight (3 parts preferred).

As has been set forth above, other thermoplastic materials such as polyethylene and nylon are satisfactory for the practice of the invention. In the case of polyethylene, the same Iblowing agents and fillers may be used as in the case of polyvinyl chloride. No plasticizer, however, will be added to the mix, the necessary degree of plas- Iticity being imparted by the `application of heat during the subsequent extrusion process. Insofar las nylon is concerned, it may be used as a direct substitute f'or polyvinyl chloride with the exceptionsy that the stabilizer will be eliminated and a compatible plasticizer such as N-ethyl oand p-toluene sulfonamide will be substituted.

In connection with polyvinyl chloride, the above discussion has been given in terms of its use in the form of a vinyl pl-astisol. yIt will be understood, however, that the mix can be produced in the form of a dry blend, i.e. a physical mixture lof polyvinyl chloride resin and plas- Additionally, it `can be used in the granular state in which the mixing of the resin and the plasticizer occur under conditions of shear and elevated temperature.

To further describe the method of my invention, one of the above mixes is then fed to an extruder (or the actual mixing may occur within the extruder itself) of any conventional type and having an l`orifice designed to produce a thread of any desired physical dimensions or cross-sectional configuration. This stage of the operar tion is carried out at a temperature that will, at a minimum, impart the desired plasticity to the mix and yet, at a maximum, will be insuicient to activate the specific blowing agent that has been incorporated into the mix or degrade the resin. l

Although it is satisfactory and within ythe scope of the present invention to extrude a thread which will consist solely of one of the mixtures described above, it is desirable -for reasons of mechanical strength and handleability of the extruded thread to extrude the mixture around a core 11 such as is shown in FIGURE 3. Such core can consist of any one of a plurality of materials such as, for example, rayon, cotton, nylon, glass, twisted paper, and various metal wires. The only criteria for the material of the core is that it shall not be destroyed either by the materials of the mix or by the extrusion temperatures to be encountered.

'Ihe extruded thread is then transferred to a weaving or knitting machine, of any conventional type, and there knitted Vor wovenV into the desired form of fabric-like material. Possible end products for the material produced by the invention are floor coverings, crash helmets, linings for cold weather clothing, upholstery, and other uses where'the properties of resiliency, heat insulation,`im pact absorption, or strength may be desired.

The extruded thread may also be laid down in random fashion and `criss-crossed back and across itself rather than having the strands interlocked as during a knitting or weaving operation. This can be done with a continuvous length of thread or a plurality of heterogeneous length threads.

Having produced by weaving, knitting, or otherwise an article in the shape of the desired final product, such article is then subjected to elevated temperatures for a time necessary to activate the specific blowing `agent contained in the mix. These temperatures will generally be in the nature of from about 260 F. to about 400 F. It will be understood that the blowing agents used will always have a minimum thermal decomposition point above the temperatures encountered during the extrusion operation to avoid premature activation thereof. The maximum decomposition point will be below that which would result in a degradation of the resin during the relatively short time periods, in the nature lof 5 minutes, involved inthe blowing operation. Subjection to the desired heat treatment will decompose the blowing agent resulting in yan evolution of gas throughout the thermoplastic thread which has been used to form the warp and woof strands of the material. Accordingly, a plurality of small cells will be formed in the thread and the thread will be expanded in diameter. As a result of the heat treatment also, the surface of the thread, consisting as it does of a thermoplastic material, will be softened. By reason of this softening coupled with the expansion of the threads, the surfaces of the warp and Woof strands will be pressed into each other at their juncture and, upon subsequent cooling, a permanent weld or bond will be formed at such place.

Reference is now made to the appended drawings, FIGURE l showing a fabric-like material, designated generally as 4, consisting of warp and Woof strands, 5 and 6 respectively. The material is shown here in the as woven condition and before further treatment. It will be noted that the material is of a rather loose weave and is relatively limp and flimsy in physical characteristics when compared with the finished article shown in FIG- URE 2.

11n FIGURE 2, the material of FlGURE l is depicted after thermal treament and activation of the blowing agent. Warp and woef strands 5 and 6 have become a cellular material and are integrally bonded together at their junctures 7, this latter'ffeature being more graphically set forth in FIGURE 3. The warp and Woof strand have expanded substantially in cross section over the identical strands shown in FIGURE l. Material 3 is now tightly woven and has acquired mechanical strengthto a marked degree over that possessed by the same material prior to the expansion step.

As a result of this treatment, therefore, there has been produced a product having the characteristics hereinfiore described, which are enchanced lover the properties of material hereto-fore known to the art. Furthermore, these properties, as a result of my invention, are introduced into an article after it has been formed into the shape of the desired final product. thereby permitting both greater control of size, shape and dimensional characteristics as well as imparting great physical strength, then can be obtained yfrom processes or in articlesV presently known.

FIGURE 4 shows an alternate form of the invention in which warp strands 5, [for example, are in the expanded condition as described above. The woof strands S of this embodiment induce an additional feature in that they comprise either an unexpanded thread of thermoplastic resin, withV or Without a core, or a thread of other suitable non-expandable material such as wire, twisted paper, rayon, cotton, or other natural or synthetic fibers. In connection with this -gure, it will also be understood that strands S can comprise and expanded material similar to the expanded material of warp strands 5, but in which the expansion has been carried out to a lesser degree. The desired amount of expansion can, of course, be controlled by controlling the amount of blowing agent in the original mix.

`FIGURE 5 shows still another form of the invention in which strand 9 is laid down at random and crisscrossed back and forth across itself rather than being knitted ior woven as shown in `FIGURES 1 4 inclusive.

arcanes This matted or felted material is then heat treated to decompose the blowing agent and weld the junctures of the strand together as has hereinbefore been described.

Other forms and variations of this invention will readily occur to those skilled in the art. Accordingly, it is intended t'hat `the scope of the present invention shall be limited only by the scope of the claims attached hereto.

I claim:

1. The method of producing a Ifabric-like material incorporating iexpansiblelthread material, wherein the thread material comprises a mixture of thermoplastic resin and a thermally activatable blowing agent, said blowing agent requiring heating to a temperature above the minimum softening temperature of the resin for activation, said method comprising the steps of: forming said thread material in unexpanded condition into a fabric having contacting thread junctures; and subsequently heating said fabric to activating temperature of the blowing agent, thereby softening said resin While the blowing agent expands the same and increases contact pressure at said junctures and said thread material form Welded areas along contacting surfaces at said junctures.

2. The method of producing a fabric-like material incorporating expansible thread material comprising a mixture of thermoplastic resin and a thermally aotivatable blowing agent requiring heating to above the minimum softening temperature of `the resin lfor activation, said method comprising the steps of: weaving a fabric comprising a set of warp strands and a set of Woof strands wherein at least one of said sets of strands includes lengths of thread formed fof said thread material in unexpanded condition, with portions of said lengths in surface contact with `one another; and subsequently heating said fabric to activating temperature of the blowing argent, thereby softening said resin While the blowing agent expands the same and increases contact pressure between the contacting surfaces and said expanded resin forms welded areas along said contacting surfaces.

3. 'l'lhfe method of producing a fabric-like material of expansible threads comprising a mixture of thermoplastic resin and a thermally activatable blowing agent requiring heating to a temperature above the minimum softening temperature of the resin for activation, said method comprising the steps of: weaving said threads in unexpanded condition into a fabric having warp `and Woof strands in surface contact with one another; and subsequently heating said fabric to activatin-g temperature of the blowing agent, thereby softening the resin while the blowing agent expands the same and increases contact pressure and the expanded resin forms welded areas along the contacting surfaces.

4. The method of pnoducing a fabric-like material incorporating expansible threadmaterial surrounding a supporting core, wherein said expansible thread material comprises a mixture :of thermoplastic resin and a thermally activatable blowing agent, said blowing agent requiring heating to a temperature above the minimum softening temperature lof the resin for activation, the core comprising a` mater-ial that is susbrtantially unaffected by temperatures encountered in the recited steps of saidV method, said method comprising the steps of: forming said thread material surrounding said core in unexpanded condition into a fabric having contacting thread junctures; and subsequently heating said fabric to activatng temperature of the blowing agent, thereby softening said resin while the blowing agent expands the same and increases oontaot pressure at said junctures and said expanded resin forms welded areas along contacting surfaces at said junctures.

5. The method of producing a fabric-like material incorporating expansible thread material surrounding a supporting core, wherein said expansible thread material comprises ya mixture of thermoplastic resin and a thermally activatable blowing agent, said blowing agent requiring heating to `a temperature above the minimum softening temperature of the resin for activation, the core comprising a material that is substantially unaffected by the temperatures encountered in the recited steps of said method, said method comprising the steps of: weaving a fabric comprising a set of warp strands and a set of weft strands, wherein at least one of said sets of strands includes lengths of said thread material surrounding said core in unexpanded condition, into a fabric having portions of said lengths in surface contact with one another; and subsequently heating said fabric to activating ternperature ofthe blowing agent, thereby softening said resin while the blowing agent expands the same and increases contact pressure between the contacting surfaces and said expanded resin forms Welded areas along the contacting surfaces.

6. The method of producing a fabric-like material of expansible threads formed of expansible thread material surrounding a supporting core, wherein said expansible thread material comprises a mixture of thermoplastic resin and a thermally activatable blowing agent requiring heating to a temperature above the minimum softening temperature of the resin for activation, the core comprising a material that is unaected by the temperatures encountered in the recited steps of said method, said method comprising the steps of: weaving said threads in unexpanded condition into a fabric hav-ing warp and Woof strands in surface contact with one another; and subsequently heating said fabric to activating temperature of the :blowing agent, thereby softening the resin while said blowing agent expands the same and increases contact pressure between the contacting surfaces and said expanded resin forms welded areas along lthe contacting surfaces.

7. The method of producing a fabric-like material cornprising the steps of: mixing a thermoplastic resin and a thermally activatable blowing agent which requires heating to a temperature above the extrusion temperature of the resin for activation; extruding said mix as a thread, forming said thread into a fabric having contacting thread junctures; and subsequently heating said fabric to activating temperature of the blowing agent, thereby softening said resin while `the blowing agent expands the same and increases contact pressure at said junctures and said resin forms Welded areas along contacting thread surfaces at said junctures.

8. The method of claim 7 in which the thermoplastic resin is selected from the group consisting of polyvinyl chloride, polyethylene, nylon, copolymers of vinyl chloride and vinylidene chloride in which the vinylidene chloride is present in an amount up to about 10%, and copolymers of vinyl chloride and vinyl acct-ate in which the vinyl acetate is present in an amount up` to about 25% 9. The method of producing a fabric-like material comprising the steps of: mixing a thermoplastic resin and a thermally activatable blowing agent which requires heating to labove the extrusion temperature of the resin for activation; extruding Vsaid material as an expansible thread; weaving a fabric comprising a set of warp strands and a set of Woof strands wherein at least one of said sets of strands comprises lengths of said expansible thread in unexpanded condition with portions of said lengths in surface contact with one another; and subsequently heating said fabric to activating temperature of the blowmg agent, thereby softening said resin while the blowing agent expands the same and increases contact pressure of the contacting surfaces and said expanded resin forms welded areas along said portions in surface `Contact with one another.

10. The method of producing a fabric-like material comprising the steps of: mixing a thermoplastic resin and a thermally activatable blowing agent which requires heating to a temperature above the extrusion temperature of the resin for activation; extruding said mix as a thread around a core formed of a material that is substantially unaffected lby heat up to the extrusion temperature of the resin; forming said thread in unexpanded condition into a fabric having contacting thread junctures; and subsequently heating said fabric to activating temperature of the blowing agent, thereby softening said resin While the blowing agent expands the same and increases contact pressure yat said junctures and the expanded resin forms Welded areas along contacting surfaces thereof at said junctures.

References Cited in the ie of this patent UNITED STATES PATENTS Rousset Aug. Knowland Sept. Miles Dec. Whitehead Feb. Briggs Oct. Wade Mar. Kastli Nov. 

1. THE METHOD OF PRODUCING A FARBIC-LIKE MATERIAL INCORPORATING EXPANSIBLE THREAD MATERIAL, WHEREIN THE THREAD MATERIAL COMPRISES A MIXTURE OF THERMOPLASTIC RESIN AND A THERMALLY ACTIVATED BLOWING AGENT, SAID BLOWING AGENT REQUIRING HEATING TO A TEMPERATURE ABOVE THE MINIMUM SOFTENING TEMPERATURE OF THE RESIN FOR ACTIVATION, SAID METHOD COMPRISING THE STEPS OF: FORMING SAID THREAD MATERIAL IN UNEXPANDED CONDITION INTO A FABRIC HAVING CONTACT- 